Off gas extraction and chemical recovery system and related methods

ABSTRACT

An off gas extraction system provides superior results to other systems for cleaning polluted soil. Off gas is extracted, followed by compression and condensation. Compression and condensation produce an off gas further treated to produce pollutant-free exhaust. A regenerative adsorber cleans the influent gas/air by adsorbing residual chemical vapor and concentrates the removed chemical vapor and reprocesses them. Conventional scrubbers are used on the back end of the system to produce a final exhaust as prescribed by environmental regulation. Methods of accomplishing the same are likewise taught including combinations and additions consistent with schemes as they evolve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application and claims fullParis Convention Priority of U.S. Utility application Ser. No.12/648,252, entitled “OFF GAS EXTRACTION AND CHEMICAL RECOVERY SYSTEMAND RELATED METHODS,” filed on 28 Dec. 2009, which is a continuation ofSer. No. 11/960,651, entitled “OFF GAS EXTRACTION AND CHEMICAL RECOVERYSYSTEM AND RELATED METHODS,” filed on 19 Dec. 2007, the contents ofwhich are incorporated by reference herein, as if fully set forth intheir entirety.

OBJECTS AND SUMMARY OF THE INVENTIONS

An off gas extraction system provides superior results to other systemsfor cleaning polluted soil and recovery of chemicals from soil. Off gasis extracted, followed by a compression and condensation. Compressionand condensation produce liquid condensates and an off gas that must befurther treated to produce pollutant-free exhaust. A regenerativeadsorber concentrates polluted off gasses, which are sent to the frontof the system. Conventional scrubbers are used on the back end of thesystem to produce a final exhaust as prescribed by environmentalregulation. Methods of accomplishing the same are similarly offered forconsideration, including methods for efficiently remediating pollutedsoil by optimizing target off gas selection and processing of the sameto achieve compliance with changing environmental regulations.

According to a feature of the present disclosure, a device is disclosedcomprising, in combination: at least one off gas extraction source; avacuum and compression module; and a vapor elimination modulecomprising: at least one condensation module to condense fluid from offgas; and a regenerative adsorbing module having a plurality of activatedalumina adsorbers. Each adsorber adsorbs pollutants from a high pressuregas and desorbs the pollutants into a low pressure gas. When the lowpressure gas holding the desorbed pollutants is returned into the atleast one condensation module or the vacuum and compression module.

According to a feature of the present disclosure, a device is disclosedcomprising, in combination: at least one off gas extraction source; avacuum and compression module comprising: (1) a vacuum source; (2) acompressor; and (3) an aftercooler; and a vapor elimination modulecomprising: (1) at least one condensation module to condense fluid fromoff gas; and (2) a regenerative adsorbing module having a plurality ofactivated alumina adsorbers. Each adsorber adsorbs pollutants from ahigh pressure gas and desorbs the pollutants into a low pressure gas.When the low pressure gas holding the desorbed pollutants is returnedinto the at least one condensation module or the vacuum and compressionmodule.

According to a feature of the present disclosure, a method is disclosedcomprising extracting an off-gas gas comprising contaminants;compressing the off-gas gas to form a high pressure concentratedoff-gas; routing the high pressure concentrated off-gas to acondensation module to form a condensate of the contaminants and a highpressure condensed off-gas, wherein condensate is routed to acontaminant recovery tank and the high pressure condensed off-gas isrouted to a regenerative adsorbing module; adsorbing any residualcontaminants from the high pressure condensed off-gas gas in theregenerative adsorbing module with a plurality of activated aluminaadsorbers to produce a substantially contaminant-free exhaust gas;desorbing the adsorbers that contain contaminant with a portion of thecontaminant-free exhaust gas at low pressure to form a concentratedcontaminated gas that is routed to the condensation module; andscrubbing the substantially contaminant-free exhaust gas with activatedcarbon to produce a clean exhaust gas.

Briefly stated, an off gas extraction system provides superior resultsto other systems for cleaning polluted soil. Off gas is extracted,followed by compression and condensation. Compression and condensationproduce an off gas further treated to produce pollutant-free exhaust. Aregenerative adsorber cleans the influent gas/air by adsorbing residualchemical vapor and concentrates the removed chemical vapor andreprocesses them. Conventional scrubbers are used on the back end of thesystem to produce a final exhaust as prescribed by environmentalregulation. Methods of accomplishing the same are likewise taughtincluding combinations and additions consistent with schemes as theyevolve

According to embodiments, there is provided a device comprising, incombination: at least one off gas extraction source; a vacuum andcompression module; and a vapor elimination module comprising: at leastone condensation module to condense fluid from off gas; a regenerativeadsorbing module having a plurality of activated alumina adsorbers;wherein each adsorber adsorbs pollutants from a high pressure gas anddesorbs the pollutants into a low pressure gas; wherein when the lowpressure gas holding the desorbed pollutants is returned into the atleast one condensation module or the vacuum and compression module.

According to embodiments, there is provided a device comprising, incombination: at least one off gas extraction source; a vacuum andcompression module comprising: a vacuum source; a compressor; and anaftercooler; and a vapor elimination module comprising: at least onecondensation module to condense fluid from off gas; a regenerativeadsorbing module having a plurality of activated alumina adsorbers;wherein each adsorber adsorbs pollutants from a high pressure gas anddesorbs the pollutants into a low pressure gas; wherein when the lowpressure gas holding the desorbed pollutants is returned into the atleast one condensation module or the vacuum and compression module.

According to embodiments, there is provided a method comprising,extracting an off-gas gas comprising contaminants; compressing theoff-gas gas to form a high pressure concentrated off-gas; routing thehigh pressure concentrated off-gas to a condensation module to form acondensate of the contaminants and a high pressure condensed off-gas,wherein condensate is routed to a contaminant recovery tank and the highpressure condensed off-gas is routed to a regenerative adsorbing module;adsorbing any residual contaminants from the high pressure condensedoff-gas gas in the regenerative adsorbing module with a plurality ofactivated alumina adsorbers to produce a substantially contaminant-freeexhaust gas; desorbing the adsorbers that contain contaminant with aportion of the contaminant-free exhaust gas at low pressure to form aconcentrated contaminated gas that is routed to the condensation module;and scrubbing the substantially contaminant-free exhaust gas withactivated carbon to produce a clean exhaust gas.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned features and objects of the present disclosure willbecome more apparent with reference to the following description takenin conjunction with the accompanying drawings wherein like referencenumerals denote like elements and in which:

FIG. 1 is a block diagram of an embodiment of an off gas extractionsystem for removing pollutant from soils;

FIG. 2 is a block diagram of an embodiment of a module for preparing anoff gas to have pollutant-laden vapor removed;

FIG. 3 is a block diagram of an embodiment of a compression/condensationsystem for condensing pollutant-laden vapor from a gas;

FIG. 4 is a block diagram of an embodiment of a regenerative adsorptionsystem;

FIG. 5 is a flow chart of an embodiment of a method for removingpollutant-laden vapor from gas extracted from soil;

FIG. 6 is a flow chart of an embodiment of a process for addressingcontaminants at a contaminated site;

FIG. 7 is a graph of an embodiment of experimental data of the system ofthe present disclosure; and

FIG. 8 is a graph of an embodiment of experimental data of the system ofthe present disclosure.

DETAILED DESCRIPTION OF THE INVENTIONS

The present inventors have discovered that existing processes andassemblies fail to manage off gas in ways consistent with remediatingcontaminated sources. Namely, as described herein, the instant systemcontemplates processing of gas holding desoched pollutants at points inadvance of vacuum and compression modules or condensation modules.“Desoching” as used herein expressly includes that which occurs aftersubject adsorbers are saturated substantially with contaminants, aswould be known to those skilled in the art. Likewise, it has beendiscovered that within the context of the instant systems, the gasholding desoched pollutants enriches the pollutant concentration of theoff gas entering vacuum and compression modules.

As used in the present disclosure, the term “off gas” shall be definedas gasses extracted from contaminated sources and includes soil vaporsand previously collected soil vapors.

The industrial revolution marked a radical change to many aspects ofsociety. Industrialized nations became increasingly productive andurbanized. Chemical production became centralized. Other industriesutilized chemicals in the production process of other goods. Increasedpollution was the result. Soil, air, and water carried unprecedentedlevels of pollutants over the last 200 years.

Nevertheless, during the middle of the 20^(th) century, socialconscience and government sought to eliminate or reduce pollution wherepossible. The United States government passed strict environmental lawsand set aside funds for cleaning polluted natural resources. Similarly,corporations and companies are taking steps to improve the nature andquality of pollutants and to address polluted natural resources.

Traditionally, pollutants trapped in the soil have been very difficultto address. Contaminated soil provides a uniquely difficult problem inthat it cannot be filtered like air or water. Rather, pollutants must bedrawn out of the soil. Generally, the process of drawing out thepollutant requires air or water and heat to be used to enable extractionof the pollutant as a vapor or liquid, which must then be quarantined orcleansed. Often, pollutants are removed from the soil by off gasextraction processes.

Soil vapor extraction (SVE), also known as “soil venting” or “vacuumextraction,” is an in situ remedial technology that reducesconcentrations of volatile pollutants. In this technology, a vacuum isapplied to wells near the source of contamination in the soil. Volatileconstituents of the contaminant mass “evaporate” and the vapors aredrawn toward and extracted through the extraction wells. Extracted vaporis then cleansed. The increased airflow through the subsurface can alsostimulate biodegradation of some contaminants, especially those that areless volatile. Wells may be either vertical or horizontal.

SVE has been successfully applied to many petroleum derived volatileorganic compounds (VOCs) as well as semi-volatile organic compounds(SVOCs). However, other chemicals present in the soil have beendifficult, if not impossible, to remove using technologies prior to thepresent disclosure. Indeed, prior technologies are unsuited forremediation of halogenated chemicals, chloromethane, and many othervolatile chemicals.

Prior technologies often rely on compression and condensation forremoval of VOCs. These systems may also be coupled with scrubbing unitsfor residual removals of contaminated vapor prior to release to theatmosphere. Usually, scrubbing units comprise granular activated carbon(GAO) traps. Once each GAO trap becomes saturated with residualcontaminant, they must be replaced and new activated carbon used.Certain regenerative systems treat GAO with steam, which removescontaminants from the carbon. For certain chemicals, such as halogenatedcompounds, the heat and water from steam results in strong hydrohalicacids. These acids are difficult to handle, involve health and safetyrisks, cause corrosion, and consequently carry with them increased costsof remediation.

Moreover, other VOCs, such as chloromethane and freon are difficult toremove in compression and condensation steps due to their lowcondensation points. Thus, to remove these types of chemicals from thegas stream, the condensation process must cool the vapor to extremelylow temperatures, which increases costs and makes prior SVE methods fordealing with these types of chemicals less attractive. Moreover,remediation sites may often contain these types of chemicals incombination with other VOCs. When contaminated vapors are not removed inthe compression/condensation step, the scrubbing units become theprimary SVE component for removing these types of VOCs. The result ismore frequent replacement of the scrubbing reagents, as well asundesirable side effects previously discussed and many others.

Moreover, regenerative processes that require heat are potentiallydangerous with VOCs that have high vapor pressures. Introducing heat inthe presence of oxygen in these situations may lead to fires andexplosions. In addition to potential destruction of hardware that mayoccur due to fires and explosions, the VOCs or dangerous byproducts mayalso be released generally into the atmosphere. Thus, a system is neededto allow SVE remediation for VOCs that are not suited to traditional VOCmethods and systems. The present disclosure addresses this need byproviding a novel enhanced SVE system and methods capable of remediationof soil containing difficult to remove VOCs.

Turning now to FIG. 1, there is shown an embodiment of a remediation andchemical recovery system 100. Remediation and chemical recovery system100 generally comprises a plurality of extraction wells 110 and SVEsystem 200. SVE system 200 comprises a number of subsystems, accordingto embodiments, including vacuum and compression module 300, vaporelimination module 400, and contaminant recovery module 500. Vacuum andcompression module 300 removes off gas from extraction wells 110,removes liquid constituents recovered in the off gas removal process,and compresses the off gas. Vapor elimination module 400 removescontaminated vapor from the gas, producing a substantially dry gas as anintermediate result. Finally, contaminant elimination module 500collects chemical vapors and scrubs the substantially dry gas forresidual contaminant.

According to an embodiment of vacuum and compression module 300 in FIG.2, contaminated vapor is removed from extraction wells 110 andtransferred via inlet conduit 302 into vacuum and compression module300. According to embodiments, water and gas are separated usinggas/water separator 310 to prevent liquid from entering compressor 330.According to embodiments, gas/water separator 310 may be, for example, a60 gallon Manchester vertical tank (Manchester Tank, Franklin, Tenn.).Gas/water separator 310 comprises an inlet connected to inlet conduit302, a gas outlet, and a liquid out.

The gas outlet is connected to inlet blower, for example a Roots typeblower (e.g., frame size 36 powered by 116 cfm at 10″ Hg, 5-10horsepower, 3 phase, totally enclosed, fan cooled (TEFC) 240/280 voltelectric motor). Blower 320 is used to create a vacuum that pulls vaporfrom extraction wells 110. Other similar vacuum creation devices may beused depending on the desired gas flow rate, etc. as known andunderstood by a person of ordinary skill in the art.

As shown in FIG. 1, the liquid inlet connects to transfer pump 360,which pumps liquid from gas/water separator 310 into initial contaminantrecovery tank 370. Generally, depending on the well configuration,little water will be extracted from extraction well 110. However, if thewater table is high, slurping may occur necessitating gas/waterseparator 310 to separate the water from the gas. According to thisconfiguration, holes are inserted into pipes at each extraction wellsite, some above that water table and some below. The vacuum pulls bothvapor and water from the well, which is then separated by gas/waterseparator 310.

Transfer pump 360 removes liquid from gas/water separator 310. Transferpump 360 may be, for example, a centrifugal, 120/230 volt, ½ horsepowermotor pump capable of moving 20 gallons per minute, according toembodiments. Naturally, extraction wells 110 that produce large volumesof water may need transfer pump 360 that is capable of pumping liquid ata more rapid rate. Similarly, extraction wells 110 producing onlynominal amounts of water may be fitted with transfer pump 360 that movesfewer gallons per minute. The exact choice of transfer pump 360 will beknown and understood by artisans.

Initial contaminant recovery tank 370 may be any tank suitable for thepurpose of collecting contaminated liquids. As described below, aspecific gravity separator may be disposed between transfer pump 360 andinitial contaminant recovery tank 370 to separate each specificcontaminant from the other contaminants, according to embodiments.

Turning back to FIG. 2, inlet blower 320 moves gas containingcontaminated vapor from gas/water separator 310 to compressor 330.Compressor may be any number of conventional air compressor systemsknown to artisans, e.g., a Quincy Model Q 5120 reciprocating compressor,94 scfm at 175 psi, powered by a 25-horsepower TEFC 240/280 voltelectric motor. Those of ordinary skill in the art will know andunderstand the applicable compressors to use based on the relevantparameters in the system. According to embodiments, air compressor 330will be able to compress gas to at least 175 psi. Compressed gascontaining contaminated vapor concentrates the contaminated vapor forlater removal in vapor elimination module 400.

After gas is compressed with gas compressor 330, gas is routed toaftercooler 350, which commences a first round of cooling for thecompressed gas containing the contaminated vapor. According toembodiments, aftercooler 350 may be comprised of a Arrow model AFC 120-1air to air cooler system (at 150 psi and 180 scfm). As gas iscompressed, temperature of gas increases substantially in compliancewith that algorithm defined by or known as the ideal gas law.Aftercooler 350 provides the initial cooling of hot gas prior to fullcondensation in vapor elimination module 400. As the hot gas cools,initial condensation may occur and an amount of contaminated vapor maycondense. The condensate is transferred from aftercooler 350 viaaftercooler conduit 355 to initial contaminant recovery tank 510.

Exhaust from vacuum and compression module 300 is directed to vaporelimination module 400 via vapor elimination inlet conduit 352.According to embodiments, vapor elimination module 400 comprisescondensation module 410 and regenerative adsorber module 450. Vapor isinitially directed to condensation module 410. In condensation module410, a great majority of contaminated vapor is condensed and caused tobe collected by primary contaminant recovery tank 510. In regenerativeadsorber module 450, residual contaminated vapor is captured and routedto the front on SVE system 200 and rerouted into vapor eliminationmodule 400; clean air from regenerative adsorber module 450 is exhaustedto activated carbon scrubbers 520 a, 520 b, 520 c.

According to an embodiment shown in FIG. 3, further differentiation ofother systems is schematically illustrated, whereby, for examplecondensation module 410 comprises a heat exchange system for reducingthe temperature of the gas containing contaminated vapor. This moduleresponds to ongoing challenges others have had in dealing with certainvolatiles which are not easily converted into the liquid phase. Theprocess causes many chemicals to condense into a liquid, which issubsequently routed to contaminant recovery module 500.

According to embodiments, condensation module 410 comprises a pluralityof heat exchanging mechanisms 412, 416. Air/air heat exchanger 412accomplishes initial cooling of compressed contaminated vapor.Importantly, air/air heat exchanger removes virtually all of the waterand water vapor in the compressed gas. After initial cooling hasoccurred, the compressed contaminated vapor is transferred toair/refrigerant heat exchanger 416 via warm vapor conduit 414. Furthercooling of the compressed contaminated vapor occurs in air/refrigerantheat exchanger 416, causing condensation of the compressed contaminatedvapor as the temperature of the gas containing the contaminated vapordrops below condensation point depending on the chemical beingcondensed. At this stage the compressed vapor is virtually dry and freeof water and water vapor, according to embodiments.

Air/air heat exchanger 412 and air/refrigerant heat exchanger 416 workin tandem to heat and cool their respective input and output gasses. Thecold output from air/refrigerant heat exchanger 416 is routed throughair/air heat exchanger 412 via cold vapor conduit 418. Warm gas incomingto air/air heat exchanger 412 from aftercooler 350 via vapor eliminationinlet conduit 352 is therefore cooled by the cold gas routed intoair/air heat exchanger 412 and the cold gas in cold vapor conduit 418 islikewise warmed by warm gas incoming from aftercooler 350 via vaporelimination inlet conduit 352.

According to embodiments, air/air heat exchanger 412 and air/refrigerantheat exchanger 416 are disposed in condensation module 410 in pairs.Typically, the pairs of heat exchangers 412, 416 work in cycles. Duringthe cooling phase in air/refrigerant heat exchanger 416, condensate ofthe compression contaminated vapors forms. Condensate will continue toform as long as refrigerant remains in air/refrigerant heat exchanger416. To remove the condensate, the air/refrigerant heat exchanger 416must undergo a thawing cycle to liquefy the condensate and remove it,which requires the refrigerant to be removed. Thus, by using pairs,first air/refrigerant heat exchanger 416 cools while the secondair/refrigerant heat exchanger 416 thaws. Once thawing is complete, therespective functions are reversed and the first air/refrigerant heatexchanger 416 thaws while the second air/refrigerant heat exchanger 416cools. Thawed liquefied contaminant is removed from heat exchangers 412,416 as would be known to artisans. The heat exchange process describedherein is accomplished, according to embodiments, in cycles to optimizeheat exchange and prevents air/refrigerant heat exchanger 416 fromfreezing up.

According to embodiments, refrigerant and warm gas to be cooled byrefrigerant are input at the same location and experiences parallel flowrather than cross flow, as known in the art. Embodiments employingparallel flow are more rapidly cooled, allowing for shorter cycle timesand improving the overall efficiency of the system. According toembodiments, cross flow configurations and parallel flow configurationsmay be chosen on a case by case basis as would be known to a person ofordinary skill in the art.

Air/refrigerant heat exchanger 416 exchanges heat as would be known to aperson of ordinary skill in the art. That is, the refrigerant providesthe cooling for the gas. The final temperature range of the gas dependson the coolant used, airflow, and other factors. According toembodiments, if a majority of contaminant condenses in air/air heatexchanger 412, then gas flow may be increased or cycle time may bedecreased as a matter of efficiency. Similarly, where contaminated vaporfails to condense at an efficient rate, gas flow may be decreased orcycle time may be increased to expose gas to refrigerant for a longerperiod.

According to other embodiments where heat exchange occurs in cycles, gasflow rate remains constant, but the duration the gas is exposed to theheat exchangers is varied. Thus, if air/air heat exchanger 412inefficiently condenses vapor, the duration in the air/refrigerant heatexchanger 416 may be increased in each cycle. Thus, variations in theoptimization of gas temperatures may likewise be effected.

According to embodiments, aftercooler 350 monitors the temperature ofthe compressed contaminated gas to deliver it to condensation module 410within an optimal temperature range for condensation cycling. Compressedcontaminated gas that is too cold will not effectively warm cold exhaustfrom air/refrigerant heat exchanger 416 and compressed contaminate gasthat is too warm will be inefficiently cooled in condensation module 410requiring cycle times to be increased to remove a substantial portion ofcontaminated vapors. Thus, tuning aftercooler to provide an optimalcompressed contaminated gas temperature prior to delivery tocondensation module 410 increases efficiency of the system and serves asan optimization step.

For example, condensed vapor leaves compressor 330 at approximately 250°F. and approximately 180 PSI. Aftercooler 350 reduces the temperaturefrom approximately 250° F. to approximately 85° F. As previouslydescribed, an initial condensate will be formed as the gas is initiallycooled in aftercooler 350. The initial condensate is transferred to aninitial contaminant recovery tank or, according to embodiments, primarycontaminant recovery tank 510 in contaminant recovery module 500.

Gas is transferred from aftercooler 350 to air/air heat exchanger 412via vapor elimination inlet conduit 352. Gas entering air/air heatexchanger is cooled from approximately 85° F. to approximately 20° F.,as the heat exchange occurs between the gas from aftercooler 350 and thecold gas from air/refrigerant heat exchanger 416. Further condensate isformed as the gas further cools to approximately 20° F. It istransferred to primary contaminant recovery tank 510 in contaminantrecovery module 500 via contaminant recovery module conduit 420,according to embodiments. Specific gravity separator 508 may be includedto separate contaminants by specific gravity and store separatedchemical contaminants in multiple contaminant recovery tanks 510.

The gas cooled to 20° F. then transfers to air/refrigerant heatexchanger 416 for further cooling to a cold gas from approximately 20°F. to approximately (−30)° F. due to the heat exchange between gas andrefrigerant, as known to artisans. As depicted in FIG. 3, refrigerationunit 430 provides refrigerant via refrigerant inlet conduit 432 toair/refrigerant heat exchanger 416 for cooling of the cold gas. Toprevent freezing up problems, gas/gas heat exchanger 412 may be cycledwith gas/refrigerant heat exchanger 416, as would be known to artisans.Thus, prior to freezing up, warmer gas from gas/gas heat exchanger 412is used to warm the cold gas in gas/refrigerant heat exchanger 416.After cooling, the refrigerant returns to refrigeration unit 430 viarefrigerant outlet conduit 434, according to embodiments. At this pointin the process, virtually all water vapor has been removed from the gas,but chemical vapors may remain due to varying dew points and vaporpressures.

According to embodiments, there is provided a device comprising, incombination: at least one off gas extraction source; a vacuum andcompression module; and a vapor elimination module comprising: at leastone condensation module to condense fluid from off gas; a regenerativeadsorbing module having a plurality of activated alumina adsorbers;wherein each adsorber adsorbs pollutants from a high pressure gas anddesorbs the pollutants into a low pressure gas; wherein when the lowpressure gas holding the desorbed pollutants is returned into the atleast one condensation module or the vacuum and compression module.

According to embodiments, there is provided a device comprising, incombination: at least one off gas extraction source; a vacuum andcompression module comprising: a vacuum source; a compressor; and anaftercooler; and a vapor elimination module comprising: at least onecondensation module to condense fluid from off gas; a regenerativeadsorbing module having a plurality of activated alumina adsorbers;wherein each adsorber adsorbs pollutants from a high pressure gas anddesorbs the pollutants into a low pressure gas; wherein when the lowpressure gas holding the desorbed pollutants is returned into the atleast one condensation module or the vacuum and compression module.

According to embodiments, there is provided a method comprising,extracting an off-gas gas comprising contaminants; compressing theoff-gas gas to form a high pressure concentrated off-gas; routing thehigh pressure concentrated off-gas to a condensation module to form acondensate of the contaminants and a high pressure condensed off-gas,wherein condensate is routed to a contaminant recovery tank and the highpressure condensed off-gas is routed to a regenerative adsorbing module;adsorbing any residual contaminants from the high pressure condensedoff-gas gas in the regenerative adsorbing module with a plurality ofactivated alumina adsorbers to produce a substantially contaminant-freeexhaust gas; desorbing the adsorbers that contain contaminant with aportion of the contaminant-free exhaust gas at low pressure to form aconcentrated contaminated gas that is routed to the condensation module;and scrubbing the substantially contaminant-free exhaust gas withactivated carbon to produce a clean exhaust gas.

According to an embodiment, the final temperature of the cold gasdepends on the length of time the gas is cooled and the refrigerant. Inair/refrigerant heat exchanger 416 final condensation occurs and thecondensate is collected after thawing and transferred to contaminantrecovery module 500 via contaminant recovery module conduit 420. The drycold gas is then transferred to air/air heat exchanger to cool incomingwarm gas from aftercooler 350 and warm the cold gas. According toembodiments, cold gas is then routed to regenerative adsorber 450 toremove residual chemical vapors via regenerative adsorber inlet conduit452.

According to embodiments, multiple condensation modules 410 may be usedin parallel or in series to improve efficiency of the condensationprocess. Those of ordinary skill in the art will understand that eachremediation site may require optimization dependant on the particularcontaminants at the site, their relative abundance, their vaporpressures, their dew points, and their specific heat of phaseconversion.

However, the prior art systems have been unable to be industriallyeffective for condensation of more challenging contaminants. The presentinvention's optimizing differentiates it from extant systems, withcondensation modules 410 used in parallel to provide for greater gasflow through the system. Conversely, condensation modules 410 may beused in series to expose contaminated vapor to subsequent condensationsteps in an attempt to remove greater percentages of total contaminantsduring the condensation step, according to embodiments.

After the condensation step, residual contaminated vapor typicallyremains in the gas due to incomplete condensation or chemicals that arenot cooled enough or for long enough for condensation to occur.According to an embodiment in FIG. 4, high-pressure gas containingresidual contaminated vapor is routed to regenerative adsorber module450 via regenerative adsorber inlet conduit 452. As shown, twoadsorption chambers 460 a, 460 b work in tandem to adsorb residualcontaminated vapor. During operation, one adsorption chamber 460 a, 460b adsorbs residual contaminated vapor while the other adsorption chamber460 b, 460 a deadsorbs contaminated vapor. The process of desorptionregenerates adsorption material 462 a, 462 b for re-adsorption ofcontaminated vapor.

According to an embodiment, an adsorption material 462 a, 462 b isactivated alumina. A person of ordinary skill in the art will readilyknow and appreciate that other, similar materials may be used inadsorption module depending on the nature of the remediation site, thechemicals involved, and goals of each remediation project. Adsorption byadsorption materials, such as activated alumina, carbon, or resins,occurs at high pressure; desorption occurs at low pressure. Othersimilar materials and materials specifically suited to adsorption ofspecific chemicals are expressly contemplated as would be known to aperson of ordinary skill in the art. Both adsorption and desorption aretemperature insensitive processes, which makes the present systemsuperior for many types of remediation, such as with halogenatedchemicals due to the lack of necessity to introduce heat and formstrongly acidic byproducts as a result in the desorption process.

Contaminated vapor is introduced to regenerative adsorber module 450 viaregenerative adsorber inlet conduit 452. Disposed between regenerativeadsorber inlet conduit and each adsorption chamber 460 a, 460 b areinlet valves 454. Inlet valve 454 control which adsorption chamber 460a, 460 b is adsorbing residual contaminated vapor and adsorption chamber460 a, 460 b desorbing contaminated vapor. During the adsorptionprocess, inlet valve 454 is in an open position allowing gas containingresidual contaminated vapor to enter adsorption chamber 460 a, 460 b andcontact adsorption material 462 a, 462 b. During the desorption process,inlet valve 454 is in a closed position to prevent gas from enteringadsorption chamber 460 a, 460 b.

During the adsorption process, gas containing residual contaminatedvapor is forced through adsorption material 462 a, 462 b in adsorptionchamber 460 a, 460 b. Adsorption material 462 a, 462 b removes vaporfrom the gas, including contaminated vapor. As vapor is removed from thegas, adsorption material 462 a, 462 b charges with contaminated vapor.Gas leaving adsorption chamber 460 a, 460 b is therefore substantiallyclean. Artisans will recognize that one of flow rate of the gascontaining contaminated vapor or cycle time will vary from remediationsite to remediation site.

Depending on the types of chemicals being removed, the concentration ofthe contaminants, the relative amount of contaminated vapor removed inprevious remediation steps, for example compression/condensation, andthe efficiency of adsorption material 462 a, 462 b in removingparticular vapors from the gas, the parameters within which the systemruns will differ. To that end, a person of ordinary skill in the artwill know and understand that flow rate or cycle time, adsorptionmaterial 462 a, 462 b, surface area of adsorption material 462 a, 462 b,and other similar variables known to artisans will be evaluated andoptimized on a per site basis. In some cases, multiple regenerativeadsorption modules 450 will be used in series to accomplish a desiredreduction in contaminated vapor passing through vapor elimination module400.

According to an embodiment where adsorption material 462 a, 462 b isactivated alumina or other materials, adsorption of vapor in gas occursat high pressure. For example and according to an embodiment, cold gasleaving condensation module 410 is at approximately 150 PSI (referringback to FIG. 1) having been compressed prior to entering condensationmodule 410. After leaving condensation module 410 and enteringregenerative adsorber module 450, gas pressure is still at approximately150 PSI.

Referring again to FIG. 4, once gas has been exposed to and causedadsorption material 462 a, 462 b to be charged with contaminated vapor,the exhaust is substantially clean. It escapes through clean exhaustconduit 472. Disposed on clean exhaust conduit 472 are clean exhaustvalves 474, according to the exemplary embodiment. Generally, at leastone clean exhaust valve 474 is disposed along clean exhaust conduit 472per adsorption chamber 460 a, 460 b, although multiple clean exhaustvalves 474 are contemplated as would be known to artisans. Clean exhaustconduit 472 releases substantially clean gas into the ambient air orroutes the substantially clean gas to scrubbers 530, according toembodiments. A back pressure regulator may be disposed prior along cleanexhaust conduit 472 to maintain a baseline of pressure in remediationand chemical recovery system 100.

According to embodiments, clean exhaust valves 474 shunts a portion ofsubstantially clean gas for the purpose of desorption. When cleanexhaust valve 474 is “closed,” it allows a small flow of clean exhaustgas to flow to charged adsorption chamber 460 a, 460 b and throughcharged adsorption material 462 a, 462 b. This low pressure flow causesadsorption material 462 a, 462 b to release the contaminated vaporscollected in the charging step. These vapors exit through exhaustconduit 470 as inlet valve 454 is closed for charged adsorption chamber460 a, 460 b as the desorption step occurs.

To that end, clean exhaust valves 474 are configured to shunt a portionof the substantially clean gas into adsorption chamber 460 a, 460 b thatis desorbing contaminated vapor. Because desorption occurs at lowerpressure, a small percentage of the total clean exhaust gas is divertedas a low pressure gas to desorbing adsorption chamber 460 a, 460 b,while the remaining substantially clean gas continues through cleanexhaust conduit 472. The process of shunting a small percentage ofsubstantially clean gas may be accomplished by partially opening cleanexhaust valve 474 or through the use of a multiple valve system, aswould be known to artisans. For example, clean exhaust valve 474 maycomprise one valve that allows low-pressure substantially clean gas topass during adsorption chamber's 460 a, 460 b desorption cycle and aseparate valve that may be fully opened to allow high-pressuresubstantially clean gas to escape during the adsorption cycle. Theimplementation of such a system will be known and understood by a personof ordinary skill in the art.

Consequently, as one adsorption chamber, e.g., 460 a, of regenerativeadsorber module 450 is being charged with contaminated vapors andexhausting substantially clean exhaust gas, adsorption chamber, 460 b isbeing desorbed of contaminated vapors previously collected and containedin adsorption material 462 b. Desorption occurs as a percentage of thesubstantially clean gas forming a low pressure flow is shunted intoadsorption chamber 460 b. After adsorption chamber 460 a becomes fullycharged, the system is reversed and adsorption chamber 460 b is chargedwith contaminated vapors while adsorption chamber 460 a is desorbed ofthe previously collected contaminated vapors.

During the desorption cycle of adsorption chamber 460 a, 460 b,adsorption material 462 a, 462 b starts in a state wherein adsorptionmaterial 462 a, 462 b is fully charged with contaminated vapor. Aslow-pressure substantially clean air is shunted into adsorption chamber460 a, 460 b, vapor contained in adsorption material 462 a, 462 b isreleased from adsorption material 462 a, 462 b into the low-pressuresubstantially clean gas. The resultant gas comprises concentratedcontaminated vapor. The gas containing the concentrated contaminatedvapor is then routed through exhaust conduit 470 to vacuum andcompression module 300 for recompression and rerouting throughcompression/condensation.

Multiple regenerative adsorber modules 450 may be placed in series or inparallel as a matter of efficiency to ensure adequate removal ofparticularly difficult contaminants. Moreover, efficiencies of thepresent system may provide for increased gas flow rates, and thus morerapid remediation of a polluted remediation site, due to increasedefficiency of remediation and chemical recovery system 100 overconventional SVE systems.

Thus, artisans will appreciate that nearly all contaminated vapor fromthe ground is eliminated by compression/condensation. Vapor that escapescompression/condensation is captured by adsorption material 462 a, 462 bfor reconcentration during the desorption process. The reconcentratedcontaminated media will then be more readily condensed out during asecond round of compression/condensation owing to the increasedconcentration of the contaminated vapor, where it would have originallyescaped due to the fact that the concentration of contaminated vapordropped below a critical point where no additional contaminated vapor ofa given chemical could be condensed out of the gas. Thecompression/condensation-adsorption cycle is repeated until the measuredvolumetric concentration output of contaminant being removed shows theremediation site is substantially clean.

Referring now also to FIG. 1, scrubbers 520 a, 520 b, 520 c may beintroduced into SVE system 200 to remove contaminated vapor that escapesregenerative adsorption module 450. Scrubbers 520 a, 520 b, 520 c may beconventional GAO traps. As shown in FIG. 1, scrubbers 520 a, 520 b, 520c may occur in series to achieve a desired gas concentration ofcontaminant. Scrubbers 520 a, 520 b, 520 c are connected to vaporelimination module 400 via clean exhaust conduit 472. The specificacceptable final concentration of each contaminant will be known to aperson of ordinary skill in the art and defined by applicableenvironmental statute. According to embodiments wherein GAO is used asthe scrubbing media, scrubbers 520 a, 520 b, 520 c will periodicallyneed to have GAO replaced once it becomes fully charged withcontaminant. After gas is scrubbed to the desired contaminantconcentration, gas is discharged to the ambient air via dischargeconduit 530.

According to an embodiment of a method for vapor extraction shown inFIG. 5, vapor is extracted from the soil of a remediation site 1010.These vapors, as previously discussed contain vapors contaminated withpollutant. After extraction, the off gas is compressed 1020 aspreviously described. Thereafter, the compressed gas is cooled in acondensation process 1030, which causes much of the contaminated vaporsto condense into a liquid form that may be captured.

Residual contaminated vapors not captured by the compression andcondensation process are routed to a regenerative adsorber 1040. Oncegas is treated in regenerative adsorber step, it is substantially clean.It is exposed to scrubbing with activated carbon 1060 to ensure thefinal exhaust is virtually clean. Prior to scrubbing, a portion of thesubstantially clean gas is routed through the regenerative adsorber atlow pressure. The regenerative adsorber collects and then releasescontaminated vapor as a concentrated vapor 1050 which is routed to thecompression step 1020.

Likewise disclosed is a method for optimizing the use of the systems ofthe present disclosures. The optimization method ensures efficient flow.Initially, plans are generated to do this based on ostensivecontainments to be addressed. These plans may be directed towardsgeneral remediation of a site, to specific contaminants, or according tothe directive of a regulatory authority, such as the United StatesEnvironmental Protection Agency. Generally, the plan will include use ofa remediation system, such as the SVE system disclosed herein. Dependingon the particular contaminants to be addressed, optimizations of theremediation will address the particular parameters of the remediationsystem.

For example, a remediation site may be contaminated with difficult toremove contaminants such as chloromethane or freon that will be removedby compression and condensation inefficiently. In these types of cases,for example, airflow, cycle time, or both may be reduced to optimizeperformance of the remediation system. In other embodiments, airflow maybe increased when compression and condensation is efficient.Additionally, the freeze and thaw cycles of the compression andcondensation modules may be varied and optimized based on the plan.Similarly, decisions may be made to use systems with multiplecompression and condensation modules and regenerative adsorber modulesin series or in parallel, depending on embodiments. Similarly, theadsorption and desorption may be cycled to adjust the system to siteconditions, as necessary and according to embodiments.

According to an embodiment of a method for addressing soil remediationas shown in FIG. 6, the site is first tested and the contaminants for aparticular site identified 1100. After determination of the types,concentrations, and relevant data regarding the contaminants, aremediation plan is developed 1110. The remediation plan details flowrates, locations for extraction of contaminated vapor, and other similarconsiderations that would be useful in formation of the remediationplan. Artisans will understand the relevant considerations in theformation of the remediation plan.

Prior to, during, or after formation of the remediation plan, the planmay be optimized 1120, according to embodiments. The optimizationprocess generally comprises the cross-referencing of the contaminants tobe removed with a database of parameters for removal of knowncontaminants. The database may be computerized or be another collectionof data regarding the parameters in which contaminants may be extractedusing a particular remediation technology. As contaminants will havevarying extraction and chemical properties, a specific set of operatingparameters for a remediation system may efficiently address a subset ofcontaminants while inefficiently addressing others. Optimization of theremediation plan will address the varying properties of the contaminantsto create an efficient removal process that addresses all of thecontaminants present without the undue waste in energy expenditure andresources associated with brute force and less efficient techniques.

After formation of an optimized remediation plan, the plan is executed1130. After and during execution of the plan, the nature and quantitiesof the contaminants removed may be evaluated 1140, resulting in a set ofdata. This set of data then may be used to satisfy regulatoryrequirements imposed by a regulatory body 1150, according toembodiments. Moreover these data may be used to evaluate the remediationplan and the progress in overall remediation of the site.

Once the contaminants are known, the preliminary plan may be optimizedusing a database of recovery parameters as provided by an entitycommissioning the site remediation or a regulatory authority. As theseparameters tend to vary by the remediation site or over time (e.g.,state and Federal environment regulations), optimization remainscurrent, and the execution of the plan occurs such that the applicableparameters are met or exceeded.

Execution occurs as would be known and understood by a person ofordinary skill in the art. For example, if the SVE system of the presentdisclosure is used, the process occurs as described herein according tothe plan and in accordance with the optimization rules.

After or during execution of the plan, the exact nature and quantitiesof the species recovered and remaining may be measured as a metric fordetermination of the successful execution of the plan. Moreover, thequality of the exhaust released from the remediation system into theenvironment may be monitored and measured. These data may then beexamined for compliance with the regulations imposed by the regulatoryauthority. Examples of regulatory authority may be environmental groups,government entities such as legislatures and enforcement agencies (e.g.,EPA), and other groups maintaining standards for environmentalremediation.

According to embodiments, recovered contaminants may be separated andreused. Recycling of pure or substantially pure contaminants reduces theneed to produce the contaminants for use in other useful applications,which further reduces environmental impact by reducing waste associatedwith the production of the contaminants. Contaminants may be separatedand reused as part of a remediation process, such as by installing aspecific gravity separator as previously described, or in an afterremediation process as would be known and understood by artisans.

EXAMPLE 1

A site was selected for remediation in southern California, wherein thesystem optimization was conducted to maximize the efficiency of the soilvapor extraction (SVE) system and expedite site cleanup. The SVE systemprimarily targeted volatile organic compound (VOC)-impacted soilsbeneath a former refrigerant plant and the immediate surrounding areas.The results that follow detail the monitoring of well cycling and adescription of treatment system performance over a 6-month period.

Pilot testing of the remedial system was initiated 3 years earlier.Full-scale operation began a year prior to the monitoring reported inExample 1. Routine system monitoring was conducted to maximizecontaminant removal while complying with South Coast Air QualityManagement District (SCAQMD) regulations and permits.

The site was constructed in 1919 to produce sulfuric acid and processspent sulfuric acid generated at an oil refinery, located west of thesite. Since that time, chemical manufacturing operations included thefollowing activities: sulfuric acid production from 1920 to 1972,phthalic anhydride manufacturing from 1963 to 1982 (the phthalicanhydride plant was demolished in 1996); and production of refrigerantsfrom 1964 to 2003.

Refrigerants were initially produced in 1964, includingchlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) such astrichlorofluoromethane (R-11), dichlorodifluoromethane (R-12),chlorodifluoromethane (R-22), and 1,1-dichloro-1-fluoroethane (R-141b).Raw materials for CFC/HCFC production included hydrofluoric acid, carbontetrachloride, chloroform, 1,1,1-trichloroethane (1,1,1-TCA), andantimony pentachloride catalyst.

Several blends of the refrigerant 1,1,2-trichlorotrifluorethane (R-113)with organics (used primarily in the electronics industry) were packagedat the site from the early 1980s through January 2003. Additionalorganic compounds including methyl alcohol, ethyl alcohol, cyclopentane,hexane, methylene chloride, isopropanol, and acetone were used in thedifferent blends. Refrigerant blending and production ceased on Jan. 31,2003. The site user implemented corrective action in the vicinity of therefrigerant plant to remove VOCs in the zone of greatest impact and tominimize future impacts to groundwater.

Various interruptions to the SVE system operation during the monitoringperiod occurred for demolition activities over the 6-month monitoringperiod. The system was shut down at one point to meet the ongoingconstruction health and safety requirements.

Previous investigations documented the presence of VOCs in soil, soilgas, and groundwater beneath the site. The highest concentrations ofVOCs, including CFCs and HCFCs, were located beneath the refrigerantplant.

SVE was selected as the preferred remedial measure after evaluatingseveral different methods and technologies. SVE is a treatment processthat is proven effective in remediating coarse-grained soils impactedwith VOCs. Physical site constraints, such as the depth of impactedsoils and site operations, were also considered in the selection of anappropriate technology.

The SVE system included a network of 12 vapor extraction wells (VEW)screened in multiple depth intervals. The system presented in thepresent disclosure was used to extract VOCs from the remediation site.

During initial pilot testing of the system, vapors were extracted fromonly one well and the condensed fluids were collected in half-tonpressure cylinders. A Department of Transportation (DOT) 2.2classification, 50,000-pound capacity iso-tanker was delivered to thesite and connected to the treatment system. This tank providedadditional capacity to allow full-scale SVE operation. The SVE systemwas expanded to extract from multiple wells and from wells with highercontaminant concentrations.

The SVE system operated under a SCAQMD permit. This site-specific permitwas issued with the following conditions addressing air emissions at theoutlet of the scrubbers:

-   -   VOC concentrations shall not exceed 3 parts per million by        volume (ppmv).    -   Carbon tetrachloride shall not exceed 1.8 ppmv.    -   Chloroform shall not exceed 0.9 ppmv.

Whenever the VOC concentration reaches 3 ppmv (as hexane), the carbon inthe scrubbers shall be replaced with fresh adsorbent.

To ensure compliance with the SCAQMD permit, the system effluent wasmonitored by organic vapor sensors that were connected to the mainsystem controls. The sensors automatically shut the system down if theeffluent concentration exceeded the SCAQMD permit limit.

The initial phase SVE system installation included the installation ofthe condensation process equipment and piping to an existing well. Basedon the radius of influence (ROI) data, it was determined that 12 wellswere sufficient to accomplish the remediation goals.

During the monitoring period, the inventor periodically visited the siteto conduct system maintenance operations, including adding oil tocompressors, emptying drums, changing cylinders, and replacing filters,tubing, gaskets, carbon, and valves.

The delivery of a 50,000-pound capacity iso-tanker to the siteimmediately prior to the monitoring period provided greater operationalflexibility and expanded product storage capacity. The full-scaleoperation strategy involves the cycling of 12 extraction wells tomaximize the system influent concentrations.

The objective was to reduce extraction well concentration to less than2000 ppmv. The outer wells were cycled periodically since demolitionactivities prevented use of other wells. FIG. 7 illustrates the systeminfluent VOC concentrations for the remediation site. As indicated, thepeaks are indicative of new wells being opened and added to the SEVsystem. As of the end of the reporting period, all system wells appearedto be near or below 2000 ppmv.

VOC mass removal during the monitoring period is shown in FIG. 8.Measurements of product removed since the system operations began arelisted in Table 5. The mass total does not include dissolved VOCsremoved in the condensed aqueous waste stream or vapor-phase VOCsadsorbed to carbon, which are considered negligible in comparison to thepure-phase product removed. The total mass recovered was calculated byweighing the iso-tank before and after each replacement. The combinedmass of solvents recovered during the monitoring period was 7,960pounds. Over the course of the whole experiment, 110,202 pounds of VOCswere removed, as shown in FIG. 8.

While the apparatus and method have been described in terms of what arepresently considered to be the most practical and preferred embodiments,it is to be understood that the disclosure need not be limited to thedisclosed embodiments. It is intended to cover various modifications andsimilar arrangements included within the spirit and scope of the claims,the scope of which should be accorded the broadest interpretation so asto encompass all such modifications and similar structures. The presentdisclosure includes any and all embodiments of the following claims.

1. A device comprising, in combination: at least one off gas extractionsource; a vacuum and compression module; and a vapor elimination modulecomprising: at least one condensation module to condense fluid from offgas; a regenerative adsorbing module having a plurality of activatedalumina adsorbers; wherein each adsorber adsorbs pollutants from a highpressure gas and desorbs the pollutants into a low pressure gas; whereinwhen the low pressure gas holding the desorbed pollutants is returnedinto the at least one condensation module or the vacuum and compressionmodule.
 2. The device of claim 1, further comprising at least oneactivated carbon residual scrubber.
 3. The device of claim 1, whereinthe vacuum and compression module comprises a compressor and anaftercooler.
 4. The system of claim 1, wherein the condensation modulecomprises an air-to-air heat exchanger and an air-to-refrigerant heatexchanger working in tandem, wherein an exhaust gas from theair-to-refrigerant heat exchanger is used to cool an intake gas into theair-to-air heat exchanger and the intake gas into the air-to-air heatexchanger is used to warm the exhaust gas from the air-to-refrigerantheat exchanger.
 5. The device of claim 1, further comprising a specificgravity separator that separates liquid pollutants into at least oneconstituent part.
 6. A device comprising, in combination: at least oneoff gas extraction source; a vacuum and compression module comprising: avacuum source; a compressor; and an aftercooler; and a vapor eliminationmodule comprising: at least one condensation module to condense fluidfrom off gas; a regenerative adsorbing module having a plurality ofactivated alumina adsorbers; wherein each adsorber adsorbs pollutantsfrom a high pressure gas and desorbs the pollutants into a low pressuregas; wherein when the low pressure gas holding the desorbed pollutantsis returned into the at least one condensation module or the vacuum andcompression module.
 7. The device of claim 6, further comprising atleast one activated carbon residual scrubber.
 8. The device of claim 6,further comprising a specific gravity separator.
 9. The system of claim6, wherein the condensation module comprises an air-to-air heatexchanger and an air-to-refrigerant heat exchanger working in tandem,wherein an exhaust gas from the air-to-refrigerant heat exchanger isused to cool an intake gas into the air-to-air heat exchanger and theintake gas into the air-to-air heat exchanger is used to warm theexhaust gas from the air-to-refrigerant heat exchanger.
 10. A methodcomprising: extracting an off-gas gas comprising contaminants;compressing the off-gas gas to form a high pressure concentratedoff-gas; routing the high pressure concentrated off-gas to acondensation module to form a condensate of the contaminants and a highpressure condensed off-gas, wherein condensate is routed to acontaminant recovery tank and the high pressure condensed off-gas isrouted to a regenerative adsorbing module; adsorbing any residualcontaminants from the high pressure condensed off-gas gas in theregenerative adsorbing module with a plurality of activated aluminaadsorbers to produce a substantially contaminant-free exhaust gas;desorbing the adsorbers that contain contaminant with a portion of thecontaminant-free exhaust gas at low pressure to form a concentratedcontaminated gas that is routed to the condensation module; and,scrubbing the substantially contaminant-free exhaust gas with activatedcarbon to produce a clean exhaust gas.
 11. The method of claim 10,further comprising separating each liquefied contaminant by species. 12.The method of claim 11, wherein at least one separated contaminant isrecycled.
 13. The method of claim 10, wherein one or more firstadsorbers are adsorbing contaminant and producing the contaminant-freeexhaust gas used to desorb contaminants from one or more secondadsorbers.
 14. The method of claim 10, wherein desorbing occurs afterthe adsorber is substantially saturated with contaminant.
 15. The deviceof claim 1, wherein the low pressure gas holding the desorbed pollutantsenriches the pollutant concentration of the off gas entering the vacuumand compression module.
 16. The device of claim 6, wherein the lowpressure gas holding the desorbed pollutants enriches the pollutantconcentration of the off gas entering the vacuum and compression module.17. The device of claim 10, wherein the low pressure gas holding thedesorbed pollutants enriches the pollutant concentration of the off gasentering the vacuum and compression module.
 18. A system including adevice as defined in claim 1, wherein each adsorber adsorbs pollutantsfrom a high pressure gas and desorbs the pollutants into a low pressuregas, and wherein when the low pressure gas holding the desorbedpollutants is returned into the at least one condensation module or thevacuum and compression module.
 19. The system of claim 18, wherein thegas holding desorbed pollutants is returned into a point before thevacuum and compression module.
 20. The system of claim 19, wherein thegas holding desorbed pollutants is returned into a point before thecondensation module.